The present invention generally relates to improving lithography by using a coating containing a cleaving compound to trim resist features. In particular, the present invention relates to using a coating containing a cleaving compound to controllably decrease the size of developed resist structures.
In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there has been and continues to be efforts toward scaling down the device dimensions on semiconductor wafers. In order to accomplish such high device packing density, smaller and smaller features sizes are required. This includes the width and spacing of interconnecting lines and the surface geometry such as corners and edges of various features. Since numerous interconnecting lines are typically present on a semiconductor wafer, the trend toward higher device densities is a notable concern.
The requirement of small features (and close spacing between adjacent features) requires high resolution photolithographic processes. In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the resist, and an exposing source (such as optical light, X-rays, or an electron beam) illuminates selected areas of the surface through an intervening master template, the photomask, for a particular pattern. The lithographic coating is generally a radiation-sensitized coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive of the subject pattern. Exposure of the coating through the photomask causes a chemical transformation in the exposed areas of the coating thereby making the image area either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer.
Projection lithography is a powerful and essential tool for microelectronics processing. However, lithography is not without limitations. Patterning features having dimensions of about 0.25 xcexcm or less with acceptable resolution is difficult at best, and impossible in some circumstances. Patterning small features with a high degree of critical dimension control is also very difficult. Procedures that increase resolution, improved critical dimension control, and provide small features are therefore desired.
The present invention provides chemical trim processes, methods of forming sub-lithographic features, and methods of treating patterned resists. The present invention also provides size reduced resist features that are particularly useful for subsequent semiconductor processing procedures. The methods of forming sub-lithographic features and treating patterned resists are conducted in a controllable manner whereby a specified size of the size reduced resist features may be achieved.
In one embodiment, the present invention relates to a method of treating a patterned resist involving the steps of providing the patterned resist having structural features of a first size, the patterned resist containing a polymer having a labile group; contacting a coating containing at least one cleaving compound with the patterned resist to form a thin deprotected resist layer at an interface between the patterned resist and the coating; and removing the coating and the thin deprotected resist layer leaving the patterned resist having structural features of a second size, wherein the second size is smaller than the first size.
In another embodiment, the present invention relates to a chemical trim process involving the steps of forming a patterned resist, the patterned resist containing a polymer having an acid labile pendent group; depositing an acid containing coating over the patterned resist, the acid containing coating comprising at least one acid and a coating material, thereby forming a thin deprotected resist layer at an interface between the patterned resist and the acid containing coating; and removing the acid containing coating and the thin deprotected resist layer thereby providing a trimmed patterned resist.
In yet another embodiment, the present invention relates to a method of making a sub-lithographic structure involving patterning a chemically amplified resist so as to have lithographic structures; contacting an acid containing coating with the patterned chemically amplified resist thereby forming a thin deprotected resist layer within the patterned chemically amplified resist; and removing the acid containing coating and the thin deprotected resist layer leaving sub-lithographic structures of the chemically amplified resist.
In yet another embodiment, the present invention relates to a chemical trim process involving the steps of forming a patterned resist, the patterned resist comprising a polymer having a base labile pendent group; depositing a base containing coating over the patterned resist, the base containing coating comprising at least one base and a coating material, thereby forming a thin deprotected resist layer at an interface between the patterned resist and the acid containing coating; and removing the base containing coating and the thin deprotected resist layer thereby providing a trimmed patterned resist.
In still another embodiment, the present invention relates to a chemical trim process involving the steps of forming a patterned resist, the patterned resist containing a polymer having an organic labile pendent group; depositing an organic compound containing coating over the patterned resist, the organic compound containing coating comprising at least one organic compound and a coating material, thereby forming a thin deprotected resist layer at an interface between the patterned resist and the acid containing coating; and removing the organic compound containing coating and the thin deprotected resist layer thereby providing a trimmed patterned resist.